Metallurgy of zinc-bearing lead sulfids with or without small admixtures of other metals.



, E. A. ASHCROFT. METALLUBGY OFHZINO BEARING LEAD SULFIDSIWI TH 0R WITHOUT SMALL ADMIXTURES OF OTHER METALS.

APPLICATION FILED APR. 9, 1910.

Patented Dec. 19, 1911.

UNITED STATES PATENT OFFICE.

EDGAR ARTHUR ASHCROFT, or SOGN, NORWAY.

METALLURGY OF ZINC-BEARING LEAD SULFIDS WITH OR WITHOUT TURES OF OTHER METALS.

li o all whom it may concern:

lie it known that I EDGAR ARTHUR AsH- c'noi-"r, subject of the King of England, residing at Sogn, Norway, have invented certain new and useful Improvements in the Metallurgy of Zinc-Bearin Lead Sulfids with or without Small Admixtures'of other Metals, of which the following is a specification.

This invention relates to improvements in the metallurgy of zinc-bearing lead sulfids with or without small admixtures of other metals.

Sulfids of metal nearly free from gangue are produced in large quantities from the -mechanical concentration of the well known Broken Hill refractory ores which are] taken here as sufficiently illustrative of similar ores which occur with slight modifications all over the world and are likewise amenable to the treatment herein described.

Two leading products from the concentrating mills are recognized in the arts to-day, viz: (a) zinc concentrates containing upward of 40% zinc and under 12% lead and some silver, and (6) lead concentrates containing upward of 50% of lead and under 12% of zinc and some silver. Also in smaller quantities. (0) Intermediate.products such as slimes and middlings of varying composition. In treating (a) the process of zinc smelting in retort furnaces is the one generally employed and the lead and silver and sulfur are either lost or very imperfectly recovered from the residues at. great expense. In treating (7)) the process of lead SIl'Klllllg is now almost universally employed and the zinc and sulfur are lost. The intern'iediate products (0') are atpresent only capable of economical treat ment by mixing with other ores in'smelting furnaces in trifling quantities or by being first converted by mechanical separation into products resembling either (a) or (7)) in composition.

The present invention has for its principal object the more economical treatment of the product (7/) or the like, but products such as (a) may also be treated without departing from the invention.

The conduct of the process is in manyirespects similar to that described in my application Serial No. 554,508 wherein a process especially suitable for treatment of the product (a) is described. In the present Specification of Letters Patent.

Application filed ,April 9, 1310. Serial No. 554,509. I

Patented Dec. 19, 1911.

case the proportion of lead sulfid present in the ore being much greater a large proportion of this may be electrolyzed direct to lead and sulfur or to lead and chlorid of sulfur by so treating the ore as to dissolve the lead sulfid in lead chlorid in, a fused state. chlorid will be hereinafter referred to as chloro-sulfid. 4

According to this invention a process of recovering lead from lead sulfid containing zinc and other sulfids consists in treating the ore with a fused metallic chlorid so as to dissolve thelead as .a chloro-sulfid and separating and electrolyzing said chlorosulfid separate from the zinc containing minerals. "Thus, the ore may be first charged into a bath of fused lead chlorid where after agitating with molten lead to extract the silver as before it is allowed to stand some time when owing to the high specific gravity of the melt the gangue and zinc sulfid present are found to float leaving a clear melt of lead chloro-sultid below which is tapped off and treated direct in the electrolytic apparatus until all the sulfur is discharged and the corresponding leadrecovered as pure metal. maining from this operation is returned to the first melting kettle and used for treating a second batch of ore and so on. The remainder of the melt (floating matter) from the first kettle may be treatedby the process described in application Serial No. 554,508 as if it were the lead-bearing inc concentrate (product a). If the low temperature process yielding chlorid of sulfur is employed for the electrolysis the produced sulfur chlorid is reacted with metal sulfids as already described to produce metal chlorids and sulfur. The process thus results in the recovery of all the lead and silver in the ore and the combined sulfur of these metals and the zinc is also recovered as a rich zinc sulfid which in this CtlSOjVlll assay about. 55% Zn and is readilytreated by known methods or salable to zinc smelters.

lnstead of lead chlorid in the first kettle rid preferably in quantity short of molecular equivalent in relation to the lead sulfid and preferably consisting of'mixed chlorids of sodium and zinc. 'In this case the mixture is so proportioned that the specific gravity of the melt is low enough to The lead chlorid re- SMALL ADMIX- This solutionv of lead sulfid in lead I allow the gangue and the zinc sulfid to sink and not float on standing. This will require in this case about 4 tons of the chlorid mixture for one ton of the product (7)) treated. The portion of ,the melt for direct electrolysis is ten drawn oil from the top and the lower portion treated as described in application Serial No. 554,508, or otherwise. Tie reactions in this case are as follows *irst lead chlorid is formed from the lead sulfid. and zinc chlorid present and more lead sulfid dissolves in the lead chlorid forming chloro-sulfid; excess of the mixture containing sodium chlorid (which should always be present) results in a mixture of low specific gravity consisting of lead zinc and sodium chlorids in which is dissolved lead sulfid. As stated above this solution of the lead sulfid takes place when the zinc chlorid in the mixture is in quantity short of the molecular equivalent in relation to the lead sulfid.

This process is economical in electric energy (about'tfvo volts being enough for the electrolysis); as compared with the ordinary smelting and refining process the rest of the steps are quite inexpensive while the recovery of the zinc and sulfur which are process constitute a most valulost in that able asset.

Theaccompanying drawing is a diagram representing one method of carrying this'invention into effect in the case where fused lead chlorid is used.

A is a mixing potprovided with a furnace B. The upper part A of the pot is suitably lined to resist the action ,of the fused melt O. The lower part A of the pot may be of iron and is adapted to contain a bath of molten lead D. The pot is provided with a rotatable agitator A The ore is charged into the mixing pot A containing fused lead chlorid over a bath of molten lead. When the molten lead has become sufficiently charged with silver it is moved to a store pot E whence it may be withdrawn to a cupeling apparatus for the removal of silver therefrom. When the operation in the mixing pot has taken place the contents are allowedto stand and the floating matter containing the gangue and zinc sulfid are withdrawn for treatment by the process described in my application Serial No. 554,508. The diagram F represents ona small scale the apparatus for treating the zinc residue. The lead product therefrom can be returned to the pot A as indicated by the arrow H. The clear melt of lead chlorid containing lead sulfid in solution is removed to an electrolytic vat G. The melt enters by the inlet Gr 2 The chlorid of sulfur or sulfur evolved passes away at the outlet Gr for recovery. The molten lead is removed through the outlet Gr at the bottom and the lead 5 chlorid remaining after electrolysis passes sulfid containing zinc and other sulfids which consists in treating the ore with a fused metallic chlorid to dissolve the lead and to form a chloro-sulfid, and separating and electrolyzing said chloro-sulfid separate from the zinc-containing minerals.

2. A process of recovering lead from lead sulfid containing zinc and. other sulfids which consists in treating the ore with a fused metallic chlorid to dissolve the lead and to form a'cliloro-sulfid, agitating the mixtures with molten lead to extract silver, and separating and electrolyzing said chloro-sulfid separate from the zinc-com taining minerals.

3. A process of recovering lead from lead sulfid containing zinc and other sulfids which consists in treating the ore with a fused metallic chlorid to dissolve the lead and to form a chloro-sulfid, agitating the mixture with molten lead to.extract silver,

allowing the mixture to stand when gangue and zinc sulfid float leavinga ,clear melt of chloro-sulfid, and separating and .electrolyzing said chloro-sulfid separate from the zinc'containing minerals.

4:. A process of recovering lead from lead sulfid containing zinc and other sulfids which consists in treating the ore with a fused metallic chlorid to dissolve the lead and to form a chloro-sulfld, agitating the mixture with molten lead to extract silver, allowing the mixture to stand when gangue and zinc sulfid float leaving a clear melt of chloro-sulfid, and separating and electrolyzing said chloro-sulfid, separate from the zinc'containing minerals, for the produc: tion of sulfur and metallic lead.

5. A process of recovering lead from lead sulfid containing zinc and other sulfids which consists in treating the ore with a fused metallic chlorid to dissolve the lead and to form a chloiosulfid, agitating the mixture with molten lead to extract silver, allowing the mixture to stand when gangue and zinc sulfid float leaving a clear melt of chloro-sulfid, and separating and electrolyzing said chloro-sulfid separate from the zinc-containing minerals, for the production of chlorid of sulfur and metallic lead.

6. A process of recovering lead from lead sulfid containing zinc and other sulfids which consists in treating the ore with'a fused metallic chlorid to dissolve the lead and to form a chlord-sulfid, agitating the mixture with molten lead to extract silver, allowing the mixture to stand when gangue and zinc sulfid float leaving a clear melt of chloro-sulfid, separating and electrolyzing said chloro-sulfid separate from the zinccontaining minerals, for the production of chlorid of sulfur and metallic lead, and returning the lead chlorid remaining after the electrolysis to the first kettle for use with a second batch of ore.

7. A process of recovering lead from lead sulfid containing zinc and V other sulfids which consists in treating the ore with a fused metallic chlorid to dissolve the lead and -to form a chloro-sulfid, agitating the mixture with' molten lead toextract silver, allowing the mixture to stand when gangue and zinc sulfid float leaving a clear melt of chloro-sulfid, separating and electrolyzing said. chloro-sulfid separate from the zinccontainin minerals, for-the production of chlorid o sulfur and metallic lead, returning the lead chlorid remaining after the electrolysis to the first kettlefor use with a second batch of ore, and reacting the chlorid of sulfur with metallic sulfids to produce metallicchlorid and sulfur. v

8. A process of recovering lead from lead sulfid. containing zinc and other sulfids which consists in treating the ore with fused lead chlorid to dissolve thethaad and to form a chloro-sulfid and separating and electro- .lyzing said chloro-sulfid separate from the zinc-containing minerals.

9. A process of recovering lead from lead sulfid containing zinc and other sulfids which consists in treating the ore with fused lead chlorid to dissolve the lead and to forma chloro-sulfid, agitating the mixture with molten lead to extract silver,. and electrolyzing said chloro-sulfid separate from the zinc-containing minerals.

elect-rolyzing said chloro-sulfid for the pro-' duction of sulfur and lead separate from the zinc-containing minerals and returning the lead chlorid remaining to the mixing pot for further treatment.

In testimony whereof I have signed my name to this specification in the presence of two subscribing witnesses.

EDGAR ARTHUR ASHCROFT. Witnesses:'

HARRY B. BRIDGE, PERCY HEWITI.

Copies of this patent may be obtained for five cents'each, by addressing the commissioner of intents,

Washington, D. 0.

40 10. A process of recovering lead from 

